This invention relates to microstrip microwave transmission lines and, more particularly, to a transmission line phase shifter which is effective, inexpensive and easy to fabricate.
There are numerous applications where a microstrip microwave transmission line is required to have a phase shifter inserted therein. For example, phase shifters are commonly used in phased array antenna systems. At the present time, electromechanical phase shifters exist which require a quadrature hybrid circuit so that a signal passes through the quadrature hybrid circuit and bounces off a variable length delay line. The bounced signal then returns through the isolated port of the quadrature hybrid circuit. Such a device operates in a reflective mode, which limits the operating bandwidth and adds complexity and cost to the design. Line stretchers are also known to exist which allow for a continuously variable phase shift using transmission, rather than reflection. However, line stretchers require more expensive hardware since they are typically telescoping coaxial structures. Accordingly, a need exists for a less expensive phase shifter.